1. Field of Art
The invention relates to the field of materials used for dental applications. In particular this invention pertains to a composite material for use as artificial teeth as well as crown and bridge veneer having low toxicity and optical index. More in particular this invention relates to a dental material mixture and method of preparing same which includes glass containing predetermined amounts of certain alkali and/or alkaline earth elements oxides having high wear resistance.
2. Prior Art
Dental materials used for veneers are well known in the art. However, some of the prior veneering materials used have a plastic base. Although plastic has been found to be easy to repair and handle, the low wear resistance characteristics provide problems in maintaining the plastic material in use for a prolonged period of time.
Other materials used for veneering include porcelain which has the advantage of durability. However, such porcelain materials are found to be brittle and difficult to repair when damaged.
In U.S. Pat. No. 3,066,112 Bowen describes the use of fused silica coupled to a resin with vinyl silane. The resin is an adduct of bisphenol A with glycidyl methacrylate or glycidyl acrylate. Chemically, the methacrylate resin is isopropylidenebis [p-phenyleneoxy (2-hydroxy-trimethylene)] dimethacrylate commonly called BisGMA. The material is described as useful in dental fillings and uses peroxide as a catalyst and an N, N-disubstituted aromatic amine as accelerator, but does not incorporate the use of alkali and/or alkaline earth elements as in the instant invention.
In U.S. Pat. Nos. 3,179,623; 3,194,783; and 3,194,784 Bowen further describes a variety of resin derivities using fused silica and useful for filling cavities in teeth. Bowen in U.S. Pat. No. 3,539,526 describes a dental filling material including barium containing glasses. However, it has been found that barium, as well as strontium, cesium, rubidium and heavier elements have a pronounced disadvantage in their toxicity as well as high index of refraction. This high toxicity causes the barium containing glass to interact with body fluids in the cavity and acts as irritants to tissues. The high index causes excessive opaqueness and does not allow for easily matching the filling material with naturally formed teeth. This may not be a decided disadvantage when used as a dental filling material as is described in the Bowen reference but is highly disadvantageous in the instant invention when the composite material is used for artificial teeth as well as crown and bridge veneer.
Chang describes a dental composite in U.S. Pat. No. 3,452,437 using glass spheres and fibers. This material is described as a tooth filling material but no mention is made as to glass containing alkali and/or alkaline earth metals of the subject invention.
Veneers being applied to crowns on anterior teeth in the dental laboratory is known in the art. Cornell U.S. Pat. Nos. 3,265,202 and 3,488,846 describes a resin system which is heat cured to produce a plastic veneer. However, the material described does not utilize a ceramic filler. Although referred to as a composite material in the patents such is not usually considered a composite material in the dental materials sense since it lacks ceramic fillers.
Lee in U.S. Pat. No. 3,539,533 describes a composite useful for filling teeth where the filler is quartz and the resins are BisGMA and bisphenol A dimethacrylate. In this reference, it is not believed that Lee provides for a silica glass containing predetermined percentages of alkaline and/or alkali metal oxides for use as artificial teeth or crown or bridge veneer.
In each of the above cited patents the application of composites is limited to filling cavities. Materials made according to each of the teachings of the cited references are not suitable for veneer restorations, as none of them can be polished to a high gloss or luster. The invention described herein has the unique capacity to take on a high gloss and reflective polish, and therefore extends the utilization of composite materials into this area of prosthetic dentistry. The material can be adapted to a cold cure or heat cure system to fill a variety of technique requirements. Additionally, the inventive composite has the convenience and ease of handling of plastics, and approaches the durability of porcelain.